1. Field of the Invention
The present invention relates to a semiconductor device. In particular, the invention relates to a semiconductor device such that reliability is increased when a lead inside a resin case housing semiconductor elements is provided integrally with the resin case.
2. Description of the Background Art
A semiconductor module wherein a plurality of power semiconductor elements, such as an insulated gate bipolar transistor (IGBT) and free wheeling diode (FWD), are housed in a resin case is known as a semiconductor device that controls a motor, or the like.
In one example of this semiconductor module, power semiconductor elements are electrically connected via solder to an electrical circuit formed of a conductive layer of a surface of an insulating circuit substrate, and a lead in a resin case is provided integrally with the resin case by transfer molding. One portion of the lead protrudes through a side surface portion of the resin case to the outside of the resin case, and is connected to an external terminal. The electrical circuit and power semiconductor elements of the insulating circuit substrate housed inside the resin case are electrically connected to the lead inside the resin case with bonding wire. Also, a sealing resin is implanted into the resin case wired with the bonding wire, and moisture or the like is prevented by the sealing resin from entering into the resin case, thus protecting the power semiconductor elements and the like.
The resin case is made of a polyphenylene sulfide resin (a PPS resin), a polybutylene terephthalate resin (a PBT resin), a polyamide resin (a PA resin), an acrylonitrile butadiene styrene resin (an ABS resin), or the like, and the lead is formed of a conductive laminate of copper, or the like, or by applying a metal plating to a conductive laminate. It is not easy to bring the material of the resin case and the material of the lead into close contact. Consequently, a slight gap may occur between the lead, integrally molded with the resin case by transfer molding, and the resin case. When this gap is formed along the lead protruding from inside the resin case to the outer side, there is concern that moisture will infiltrate the resin case from the exterior, leading to a decrease in the reliability of the semiconductor module.
Also, it is not easy to closely contact the resin case and lead, so that, when a slight gap occurs between the lead and resin case, it is difficult to obtain a good joint when joining the bonding wire to the lead using an ultrasonic tool.
As a heretofore known resin sealed semiconductor device, there is a semiconductor device wherein, in order to prevent an ingress of moisture from a gap in the interface of an insulating resin package and a metal support plate, a ring-like groove portion is formed in the metal support plate, and the entrance of the ring-like groove portion is of a form shorter than a bottom edge portion (JP-A-2000-236048). Also, there is a semiconductor device wherein, in order to improve the adhesion between a lead frame and sealing resin, a silver plating coating such that crystal irregularities are formed is provided on a lead frame surface (JP-A-2010-199166). Furthermore, there is a semiconductor device wherein, by an internal terminal provided in the resin case, which is fixed by being sandwiched from a side surface to the upper surface of the internal terminal by a projection formed integrally with the resin case, reliability when bonding is increased (JP-A-2000-332179).